Choose distillation or chromatography from the mixture
Diperkenalkan| English | Makna |
|---|---|
| distillate/ˈdɪstɪleɪt/ | distilat |
| chromatography/krəʊməˈtɒɡrəfi/ | kromatografi |
What would explain this observation?
- Recovering pure water from salt solution needs the water collected, whereas crystallisation aims to recover salt. The product wanted determines the method.
Build the model
- Simple distillation heats a solution so the volatile solvent vaporises, then cools its vapour in a condenser to collect liquid distillate 馏出液.
- Non-volatile salt stays in the flask.
- Fractional distillation separates miscible liquids with different boiling points using repeated vaporisation and condensation in a fractionating column.
- The lower-boiling component is enriched in vapour reaching the top; separation is not necessarily perfect.
- distillate: Liquid collected after vapour is condensed during distillation.
- chromatography 色谱法: A separation method based on different distributions between stationary and mobile phases.
Which method is suitable for collecting water from salt solution?
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Distillation boils the water off and condenses the vapour, collecting pure water and leaving the salt behind. Filtration cannot catch a dissolved solute, and salt is not magnetic.
Match each technical term to its precise meaning.
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Use the definitions to distinguish related quantities and processes.
Choose evidence that can test it
- Paper chromatography separates soluble components according to their different distributions between the moving solvent and the paper.
- Draw the baseline in pencil above the solvent level, place a small sample spot and let solvent rise.
- Components that spend more time in the mobile phase generally travel farther under these conditions.
- Compare spots with known standards using the same solvent and paper; a single spot alone does not prove purity under every possible method.
In the lab: For school-supervised distillation, use a risk-assessed apparatus with an open receiving path, never a sealed heated system. Cooling water enters the lower condenser connection and leaves the upper one. Avoid flames with flammable solvents. In chromatography, keep the lid on the vessel as appropriate, mark the solvent front before it dries and measure all distances from the same baseline. Interpretation of Rf is developed in Chemical analysis, 4.8.1.3.
Which two habits make the investigation or model in this case more defensible?
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Stating the conditions and assumptions lets others repeat the work exactly, and recording the supporting evidence lets them check the conclusion. Hiding disagreeing results removes the evidence that could challenge a wrong conclusion, and one measurement can never establish a wider claim.
Work from known quantities
- Known: a model distillation starts with 60 cm³ salt solution and collects 42 cm³ water.
- Collected volume/starting solution volume = 42/60×100 = 70%.
- This is a volume-recovery comparison, not evidence of 70% purity or a mass balance.
- In a supplied chromatogram, a dye travelling 30 mm while the front travels 50 mm has Rf = 30/50 = 0.60.
Your turn: A dye travels 24 mm and the solvent front 40 mm from the baseline. Calculate Rf.
A dye travels 24 mm and the solvent front 40 mm from the baseline. Calculate Rf.
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The result is 0.6 . Known: dye travels 24 mm; solvent front 40 mm. Use Rf = distance by dye / distance by front. Rf = 24/40 = 0.60. Rf has no unit and never exceeds 1.
Check the conclusion and its limits
- A condenser liquefies vapour; it does not filter salt.
- Fractional distillation concerns boiling-point differences, not density ranking.
- A chromatogram baseline under solvent can let the sample dissolve directly into the reservoir.
- The method does not create new dye substances.
Not true: Fractional distillation separates liquids solely because they have different densities. Fractional distillation separates by BOILING POINT: the lower-boiling liquid vaporises first. Liquids of similar density but different boiling points separate easily, so density cannot be the criterion.
- Simple distillation heats a solution so the volatile solvent vaporises, then cools its vapour in a condenser to collect liquid distillate.
- Paper chromatography separates soluble components according to their different distributions between the moving solvent and the paper.
- Watch for: A condenser liquefies vapour; it does not filter salt.
Fractional distillation separates by BOILING POINT: the lower-boiling liquid vaporises first.
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True. Fractional distillation separates by BOILING POINT: the lower-boiling liquid vaporises first. Liquids of similar density but different boiling points separate easily, so density cannot be the criterion.
Liquid collected after vapour is condensed during distillation: write the technical term.
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distillate means Liquid collected after vapour is condensed during distillation.